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st: RE: Evaluating a set of conditions


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Evaluating a set of conditions
Date   Thu, 17 Jun 2010 00:53:32 +0200

<>

" but I hardly ever use them because  
understanding them (or remembering them) usually takes longer then  
writing the 'lengthy' qualifiers."


-cond- and -inrange- are among the most easily understood functions in
Stata, if you want my take on this. Try Nick and coauthor`s
http://www.stata-journal.com/sjpdf.html?articlenum=pr0016 tutorial on -cond-
or http://www.stata-journal.com/sjpdf.html?articlenum=dm0026 on -inrange-. 

Also, you can multiply expressions which can be handy. So if you want the
running sum only for the cars with bad to average repair record:

***
sysuse auto, clear
sort rep78
gen newvar=sum((rep78<=3)*price)
l rep78 price newvar
***




HTH
Martin


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Thomas Speidel
Sent: Donnerstag, 17. Juni 2010 00:41
To: statalist@hsphsun2.harvard.edu
Subject: st: Evaluating a set of conditions

I realize this is a very broad question and no one solution can fit  
all problems. I am looking for more efficient or elegant alternatives  
to evaluate a set of conditions in Stata, than a lenghty if qualifier.  
E.g.:

do something if A==1 & (B>2 & B<.) & (C==1 | D!=2)

these expression can become lengthy and one can think of more elegant  
ways to come to the same results.
cond and inrange are the first things that come to my mind that may  
(or may not) simplify the problem, but I hardly ever use them because  
understanding them (or remembering them) usually takes longer then  
writing the 'lengthy' qualifiers.
To complicate matters one has to account for missing values.   
Admittedly, this question came about from the recent topic on missing  
values.
If someone want to share an example, please do so.

-- 
Thomas Speidel

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